An optical modulator is used to modulate radio frequency signals onto an optical carrier output by a laser to form optical signals, wherein the optical modulator is widely applied in the fields of optical fiber communication and optical fiber sensing. An output curve of the optical signals modulated by the optical modulator has a waveform of a cosine function shape. To control the optical modulator at different working points, a bias voltage may be output to the optical modulator.
However, since the optical modulator is extremely sensitive to changes of the working environment, such as changes of temperature, changes of humidity, mechanical vibration and the like. Due to the changes of the working environment, the output curve of the optical modulator is shifted, and thus the working points are shifted, so the normal operation of the optical modulator at different working points may not be ensured. Therefore, bias voltages applied to the optical modulator needs to be changed based on the changes of the environment, which is referred to as the bias voltage control technology.
In the prior art, the bias voltage control technology is developed mainly based on the solution of analog circuits. The essence thereof lies mainly in that when a bias voltage is output, a dither signal is simultaneously output, and the working point of the optical modulator is slightly adjusted according to the dither signal.